Patent GB-379289-A (GB)
Title: Improvements in disc sound record reproducing apparatus
IPC: G11B3/60
Filed: 1931-05-18
Abstract: 379,289. Gramophones. POLLUXMOTOREN-VERTRIEB GES., 2A, Antonstrasse, Albertplatz, Hochhaus, Dresden, Germany. May 18, 1931, No. 14640. Convention date, Feb. 20. [Class 40 (ii).] Relates to gramophones of the kind having a driving mechanism arranged in a flat casing the cover of which serves as the turntable. According to the invention, a holder which carries a pick-up supporting arm is adapted to be detachably secured to the casing. The apparatus is enclosed in a casing 1 having a cover 11, Fig. 1, which forms the turntable and is rotatably disposed on a spindle 26, Fig. 2, provided with a bore 27 adapted to receive an existing gramophone turntable spindle, so that the apparatus may, if desired, be mounted on an ordinary gramophone after removal of the old turntable. The electric motor 2 has magnets 44, 45 which are interconnected by a frame 32 which is supported by elastic holders 49, 50 which are connected by insulating discs with the base 53 of the casing. In this way vibrations and noises set up by the motor 2 are not transmitted therefrom. The armature 43 is connected by a flexible shaft 56 having a silencing coupling 58, to a governor 12. The armature shaft 64 carries a collector 65 which is engaged by brushes 66, 67, the ends of which are broad enough to cover at least two bars of the collector 65 at a time whereby the formation of sparks is rendered harmless by returning them to the supply network so that no disturbance is produced which could injuriously affect any nearby radio receiving set. In the circuit leading from a supply plug 70 to the motor 2 a manually-operated switch 71 and an automatic cut-out 72 are interposed. The cut-out 72 comprises a wire-strap 73, the free end 74 of which is adapted to engage with an arm 75 supporting the electric pick-up 76 while its other end extends into an electric switch box 77 in which is a braking bolt 95. At the end of reproduction from a record the strap 73 will have been turned through a sufficient angle to release the bolt 95, which is then spring- pressed into contact with the turntable at the same time as the cut-out 72 is operated to open the driving motor circuit. The arm 75 and switch box 77 are detachably connected with the casing 1 by a bayonet joint. For this purpose the casing 1 is provided with a pad 79 having a bore 80, provided with recesses 81, 82, as shown by the sectional elevation of Fig. 4. The holder 78 has a pin 83 corresponding to the bore 80, and noses 84, 85 which are adapted to engage in the recesses 81, 82. From the switch-box 77 wires lead inside the holder 78 to the pin 83. One of these conductor wires is electrically connected to a contact ring 87 mounted on the pin 83 and insulated from it while the other conductor wire passes through the pin 83 and terminates in the top 88 which is also insulated from the pin. The circuit of the electric pick-up is established by causing the contact ring 87 during insertion of the pin 83 to engage a contact 89, while the tip 88 strikes a contact spring 90. To shield the pick-up from the magnetic field of the electric motor 2 dynamo iron sheets 91 are employed. The Specification as open to inspection under Sect. 91 (3) (a) refers to Specification 375,307 and states also that further security against interference through high frequency currents produced by sparking is afforded in that the frame 32 is electrically connected with the casing 1, which is connected in parallel over condensers 68 with the supply circuit. This subject-matter does not appear in the Specification as accepted.